The identification of an optimal cell type to drive robust cardiac myogenesis is critical for improving cell-based therapy and to develop human cardiomyocyte models for heart failure. Recent studies in the Chien lab have allowed the identification, purification, and renewal of multipotent Islet-1 cardiovascular progenitors from both murine and human embryonic stem (ES) cells and inducible pluripotent stem cells (iPS). Utilizing a novel two color reporter system, a unique subset of completely committed, self-renewing cardiomyogenic progenitors (CMPs) have been isolated from ES cells, and used to generate thin films of cardiac muscle via tissue engineering. The Melton lab has recently developed novel protocols for the high efficiency generation of iPS cells from murine and human skin fibroblasts using just two genes and a chemical agent, while the Chien/Wu labs have effectively purified heart progenitors from iPS cell sources, documenting the feasibility for generating autologous human cardiovascular progenitors from iPS sources from an individual patient for cell based therapy and/or for the generation of human cardiac muscle cell-based models of cardiac disease, which should allow the use of an arsenal of genetic tools to identify the molecular pathways for cardiac muscle dysfunction. This proposal integrates unique expertise, reagents, and protocols from three leading laboratories: heart stem cell biology in development and disease (Chien);human ES and iPS technology (Melton);and cardiac muscle tissue engineering (Kit Parker). Accordingly, the Specific Aims of the two proposed projects are: Project 1: Multi-potent Islet-1/Nkx2.5 heart cell progenitors and the formation, renewal, and differentiation of committed cardiomyogenic progenitor (CMP) lineages: 1) Characterization of committed cardiomyogenic progenitors(CMPs) of the Islet-1/Nkx2.5 family of heart progenitors;2) Generation of functional heart muscle strips from CMPs of the Islet-1/Nkx2.5 family of heart progenitors; 3) Identification of Pathways which drive the formation, renewal, survival, and differentiation of committed cardiomyogenic progenitors of the Islet-1/Nkx2.5 family (Wnt/Beta Catenin, Creb312, etc.);4) Identification, purification, and characterization of the conduction system progenitors of the Islet-1/Nkx2.5 family of heart progenitors; Project 2: Generation of mouse and human heart progenitor derived models of human cardiac diseases: 1) Purification and characterization of human multipotent Islet-1/Nkx2.5 progenitors and their cardiomyogenic lineages derived from human ES and iPS cells;2) Generation and characterization of functional mouse and human heart muscle strips from multipotent Islet-1/Nkx2.5 progenitors and their cardiomyogenic lineages derived from ES and iPS cells;3) Generation and characterization of murine and human heart muscle strips from ES and iPS cells that harbor cardiomyopathic mutations. .